1. Field of the Invention
The subject invention relates generally to a heat exchanger, and, more specifically, to a heat exchanger of the type including a plurality of fluid tubes extending between an inlet header and an outlet header for transferring fluid from the inlet header to the outlet header.
2. Description of the Prior Art
Heating systems for automobiles have traditionally relied upon engine coolant as the sole heat source for providing comfort heating to the occupants of a vehicle. In such heating systems, a heat exchanger is generally used to transfer heat from the engine coolant to a second fluid, generally air. An example of such a heat exchanger is disclosed in U.S. Pat. No. 1,684,083 to S. C. Bloom.
The Bloom patent discloses a pair of headers each extending between a pair of header ends and defining a cavity. Each of the headers defines a plurality of header slots spaced from one another between the header ends thereof. A plurality of fluid tubes each extend between the headers from one of the header slots of each header to fluidly interconnect the cavities defined by the headers. A first fluid, generally an engine coolant, may flow through one of the cavities defined by one of the headers and through the fluid tubes and through the other of the cavities defined by the other of the headers, and a second fluid, generally air, may flow across the fluid tubes for transferring heat from the first fluid to the second fluid.
The heating capacity of a heat exchanger as disclosed by the Bloom patent is generally limited by the temperature of the engine coolant. Accordingly, with the advent of more efficient internal combustion engines, the amount of heat available from the engine coolant for comfort heating is reduced. As a result, three-fluid heat exchangers have been developed to add another heat source to increase the amount of heat available for comfort heating. Examples of such three-fluid heat exchangers are disclosed in U.S. Pat. No. 4,002,201 to Donaldson and U.S. Pat. No. 5,884,696 to Loup.
The Loup patent discloses a pair of first headers each extending between a pair of first header ends and defining a first cavity. Each of the first headers are disposed in a spaced relationship to one another. A pair of second headers each extending between a pair of second header ends and defining a second cavity are each disposed adjacent one of the first headers. Each of the headers defines a plurality of header slots spaced from one another between the header ends thereof. A plurality of first fluid tubes each extend between the first headers from one of the header slots of each first header to fluidly interconnect the first cavities defined by the first headers. A plurality of second fluid tubes each extend between the second headers and adjacent the first fluid tubes from one of the header slots of each second header to fluidly interconnect the second cavities defined by the second headers. A first fluid may flow through one of the first cavities defined by the associated first header and through the first fluid tubes and through the other first cavity defined by the other first header, a second fluid may flow through one of the second cavities defined by the associated second header and through the second fluid tubes and through the other second cavity defined by the other second header, and a third fluid may flow across the fluid tubes for transferring heat from the first and second fluids to the third fluid.
The Donaldson patent discloses a heat exchanger similar to that as disclosed by the Loup patent except wherein the second fluid tubes are interleaved with the first fluid tubes.
The three-fluid heat exchangers as disclosed by the Loup patent and the Donaldson patent provide for an increased amount of heat for comfort heating by transferring heat from a first and second fluid to a third fluid, however, such patents essentially comprise two heat exchangers functioning independently of one another which are placed adjacent one another thereby increasing the size of the heat exchanger. Accordingly, there remains a need for a heat exchanger which provides an increased amount of heat but which does not have an increased size.